1. Field of the Invention
The present invention relates to apparatus for direct visualization of body passages and, in particular, to an automated angioscopy imaging system that provides pulsatile irrigation coupled with synchronous real time imaging.
2. Discussion of the Prior Art
It is well-known that optical scopes may be used for direct visualization of body passages. For example, endoscopes are used for viewing the gastrointestinal tract, bronchoscopes are used for viewing bronchial passages, and arthroscopes are used for joint examination. These scopes are moved to a position within the body that the viewer desires to examine. The body passage is then visualized directly through the eyepiece of the scope or a video camera is attached to the scope to display the image on a video monitor.
An angioscope is used for viewing both the arterial and the venous systems. In the angioscopy procedure, a fiberoptic scope is inserted into the vessel through an incision and then threaded through the vessel to provide visualization at selected points along the length of the vessel. Sterile saline flush solution is introduced continuously into the vessel to provide a clear visualization field.
Angioscopy is a particularly difficult procedure in the arterial system. The pressure and the flow rate of the blood are much higher in the arteries than in the veins, making it difficult to obtain the clear, bloodless field required for the desired quality of visualization. If only a small amount of saline is used to flush away the blood, this flush is washed away too quickly to allow adequate visualization. On the other hand, if a larger amount of flushing solution is used, over a time period sufficient to allow adequate visualization, complications will arise. First, fluid overload of the patient will occur, causing electrolyte imbalance or congestive heart failure. Second, there will be a lack of perfusion to the tissue supplied by the artery undergoing angioscopy because the flushing fluid has cleared away the oxygen-carrying blood. This problem is particularly difficult in angioscopic evaluation of the coronary arteries, since the cardiac muscle cannot tolerate prolonged ischemia. Balloon occlusion may be used, but it too may cause ischemia.
Therefore, it would be highly desirable to have available an angioscopy system that provides clear visualization within the irrigation constraints described above.